Commercial products such as low-E coatings used for solar energy management effectively block large amounts of infrared (IR) radiation but fail to block significant amounts of ultraviolet (UV) radiation. Meanwhile, coatings specifically designed to block UV radiation tend to be fairly transparent to IR radiation. Thus, there is a need in the art for a coating which is effective at blocking significant amounts of both IR and UV radiation.
A coating sol comprising zinc antimonate is known in the art, under the tradename Celnax. For example, see Nissan Chemical's website at www.snowtex.com/celnax.htm for the absorption spectrum of Celnax sol (zinc antimonate sol) which is mixed with a resin. The nanoparticles of the antimony double oxide absorb significant amounts of IR, while allowing a good portion of UV and significant amounts of visible radiation to transmit therethrough. For example, see U.S. Pat. No. 6,149,888, the disclosure of which is hereby incorporated herein by reference. Thus, unfortunately, this coating is not good at blocking IR radiation. It would be desirable if such coatings could be designed so as to improve blockage of UV radiation.
U.S. Ser. No. 11/229,837, filed Sep. 20, 2005 and hereby incorporated herein by reference, discloses a composite oxide coating that efficiently blocks both UV and IR radiation, e.g., a colloidal electro-conductive oxide solution having infrared (IR) and ultraviolet (UV) blocking characteristics may be used in forming the coating. In Ser. No. 11/229,837, a substantially transparent composite oxide coating is provided that includes a silica matrix, zinc antimonate, and a UV blocking material, thereby permitting the sol after application to block significant amounts of both IR and UV radiation. The UV and IR blocking coating may comprise each of cerium oxide and zinc antimonate in the form of nanoparticulate, and silicon oxide (e.g., SiO2) formed from precursor materials such as silane(s). It has surprisingly been found that such coatings of Ser. No. 11/229,837 are effective at blocking both UV and IR radiation as shown in FIG. 1. In certain example embodiments of Ser. No. 11/229,837, the coating sol from which coatings are formed comprises from about 15 to 50% cerium oxide (more preferably from about 20 to 45%, and most preferably from about 30 to 40%), from about 30 to 70% zinc antimonate (more preferably from about 35 to 65%, and most preferably from about 40 to 55%), and from about 5 to 35% silicon oxide (more preferably from about 10 to 30%, and most preferably from about 12 to 25%). It has been found that these amounts of such materials in the coating sol provide a coating that is effective at blocking both UV and IR radiation.
In Ser. No. 11/229,837, a coating sol was coated on a substrate, and its transmission characteristics measured as shown in FIG. 1. In FIG. 1, the coating sol was applied to a glass substrate and included cerium oxide and zinc antimonate in nanoparticulate form, and silicon dioxide, in amounts of 47 mole % zinc antimonate, 36 mole % cerium oxide and 17 mole % SiO2. When this sol was applied to a glass substrate at a thickness of about 2 microns, the coated article yielded average UV transmission in the range of 300-380 nm of about 10% as shown in FIG. 1. When the cerium oxide was not present (see comparative example CE in FIG. 1), the UV transmission was undesirably higher. Different cure temperatures for the coating on the glass substrate are shown in FIG. 1 for the Example of Ser. No. 11/229,837 and the CE. Thus, in Ser. No. 11/229,837 a single layer coating is provided that blocks significant amounts of both IR and UV radiation.
Unfortunately, in certain situations the single layer coating of Ser. No. 11/229,837 may not be desirable because of the need to mix zinc antimonate, cerium oxide and SiO2 in a single layer. In particular, this technique may suffer from incompatibility of mixing the different materials (e.g., instability of dispersions, formation of single phase materials, etc.) and thus may be limited to use of only certain combinations of materials to produce single layer coatings with both IR and UV blocking properties.
In certain example embodiments of this invention, there exists a need in the art for more efficient coating capable of blocking significant amounts of both IR and UV radiation. In certain example embodiments, a heat resistant coating is provided that may be processed (e.g., thermally tempered) cost effectively with minimal steps.
In certain example embodiments of this invention, there is provided a method of making a coated article, the method comprising: forming a low-E coating on a glass substrate, the low-E coating comprising at least one infrared (IR) reflecting layer located between at least first and second dielectric layers; applying a wet coating comprising titania and ceria on the glass substrate over the low-E coating, curing the wet coating solution to form a UV blocking coating on the glass substrate, the UV blocking coating comprising a mixture of oxides of cerium and titanium.
In certain example embodiments of this invention, there is provided a method of making a coated article, the method comprising: forming a low-E coating on a glass substrate, the low-E coating comprising at least one infrared (IR) reflecting layer located between at least first and second dielectric layers; applying a wet coating comprising at least one UV blocking oxide and/or at least one precursor of a UV blocking oxide on the glass substrate over the low-E coating, forming a UV blocking and IR blocking coating on the glass substrate and subjecting the coated glass substrate to a heat treatment process including temperatures of at least about 580 degrees C. In certain example embodiments, the wet coating comprises at least one metal oxide from the group consisting of ceria, titania, zinc oxide, bismuth oxide, tin oxide and antimony oxide, and/or a precursor of at least one of these metal oxides. In certain example embodiments, the UV blocking coating comprises: titanium oxide: from about 0-50%, cerium oxide: from about 40-98%, and silicon oxide: from about 5-50%.
In certain example embodiments, the UV blocking coating comprises: titanium oxide: from about 5-50%, and cerium oxide: from about 40-98%. In certain example embodiments, the UV blocking coating comprises: titanium oxide: from about 5-20%, and cerium oxide: from about 60-95%. In certain example embodiments, the coated article has a transmission at 600 nm of at least about 60%, or at least about 70%. In certain example embodiments, the coated article has a transmission at 1700 nm of no greater than about 30%.
In certain example embodiments of this invention, there is provided a method of making a coated article, the method comprising: forming a low-E coating on a glass substrate, the low-E coating comprising at least one infrared (IR) reflecting layer located between at least first and second dielectric layers; applying a wet coating comprising a silane and ceria on the glass substrate over the low-E coating, curing the wet coating to form a UV blocking coating on the glass substrate, the UV blocking coating comprising a mixture of oxides of silicon and cerium.
In other example embodiments of this invention, there is provided a coated article comprising: a glass substrate; a low-E coating provided on the glass substrate; a UV blocking coating provided on the glass substrate over at least the low-E coating; and wherein the UV blocking coating comprises cerium oxide and at least one of silicon oxide and titanium oxide.